With proposal of a concept of pseudolite and continuous improvement of hardware technology thereof, a pseudolite positioning system has found its application in aspects such as indoor application, underground application, flight navigation, Mars probing, etc. A pseudolite may team up with a space orbit navigation positioning satellite in multiple modes, forming a system for positioning and navigation. A pseudolite notably features a low elevation angle, and a signal not required to pass through the Ionosphere. With such a satellite with a low elevation angle, the combination of a space orbit navigation positioning satellite and a pseudolite may effectively improve a geometrical structure, increasing accuracy in vertical positioning. In a special case, a pseudolite may even completely replace a space orbit navigation positioning satellite and perform independent positioning. The fundamental of pseudolite positioning (that is, positioning by pseudolite) still lies in use of a double-difference method as in relative positioning by a space orbit navigation positioning satellite. Reliability and accuracy of such a method may depend on both hardware equipment and geometrical configuration of a pseudolite.
An existing solution for implementing a pseudolite positioning system may be as follows, for example.
US patent application of Publication No. U.S. Pat. No. 6,597,988 (titled “Network assisted pseudolite acquisition for enhanced GPS navigation”) has disclosed a system including
a pseudolite location database storing information on a location of at least one pseudolite and the at least one pseudolite deployed in a certain area; and a method for sending a satellite positioning receiver at least part of the information in the pseudolite location database containing at least part a pseudolite location information;
the pseudolite location database is read by a cellular phone base station; communication with the positioning receiver is through a cellular mobile communication system; in implementation a pseudolite location is sent to the cellular mobile communication system; information for codeword search is sent to the satellite positioning receiver before positioning;
the communication may also be unidirectional broadcast; the unidirectional broadcast may be implemented by a frequency modulated broadcast station.
An interface for a satellite positioning receiver may be configured for inputting pseudolite information, local pseudolite information is used selectively by a satellite positioning receiver; the interface is separate from an antenna for receiving a satellite positioning signal; the local pseudolite information may include a number of a pseudo random sequence used by a pseudolite and a position of the pseudolite.
In an actual application, a cellular base station may be required to periodically send information on geographical coordinates and pseudo-random codes of pseudolites as required by a pseudolite positioning receiver, which may occupy lots of downlink capacity of the cellular base station.